3i6 



STRUCTURE OF SELAGINELLA 



species the leaves are arranged in four rows, two comprised of small 

 leaves situated on the upper side of the stem, and two rows of 

 large leaves towards the lower side (Fig. i8o, A and B) ; at 



each node there 

 is one large and 

 one small leaf. 

 The British 5. 

 s p ino s a, and 

 other species in 

 which the habit 

 is erect, however, 

 possess leaves 

 that are all ahke 

 (Fig. i8o, C). 



In many Ss- 

 lagi iiellas the 

 method of root- 

 ing is peculiar, 

 the roots arising 

 from special 

 leafless branches 

 kno\'\-n as rhizo- 

 phores (Fig. iSo, 

 A, rh.). These 

 are formed in 

 pairs at thepoinis 

 of forking of the 

 stems, but usu- 

 ally only one 

 member of each 

 pair develops. 

 This gro\\'s down- 

 wards, generally 

 forking r e - 

 originate from the 



Fig. 179. — Lycopodiuin. A, Small part of a plant 

 of L. davatum, with a fertile shoot bearing two 

 cones. B, Single sporophyll of same, with a 

 dehiscent sporangium. C, Prothallus of L. 

 clavalntii. D, Longitudinal section of sporophyll 

 with sporangium. E, Spore. (B after Stras- 

 burger ; C after Bruchman ; the rest original.) 



peatedly, and, on reaching the soil, root 

 swollen tips of the ultimate branches. 



The stem is traversed b}' one or few steles,- essentiall)' like 

 those of Ferns, except that each is surrounded by an air-space. 



' One in 5. spiiipsn. tbroc in 5. Itiniissiaiia. 



